The United States stepped up preparations to attack. More than 200,000 American, British and Australian troops were arrayed around Iraq, primed to fight. They readied bombs, guns, thousands of aircraft and tens of thousands of precision-guided munitions as the White House warned that the conflict may not be a short one.

In Washington, Bush's senior aides said the president met with Defense Secretary Donald H. Rumsfeld and other top military advisors to go over last-minute planning.

A Pentagon official said the plans included sending special units of troops and intelligence operatives into Iraq soon after the fighting began to fan out across the country and hunt for chemical and biological weapons.

The troops have been trained to handle such weapons, the official said, and the operatives were experts from the Defense Intelligence Agency equipped with sensors to detect nerve gas and other deadly agents.

They would try to find such weapons "sooner rather than later," the official said, moving quickly to suspected weapons sites, even though information about those sites is incomplete. The official likened the mission to a high-stakes scavenger hunt.

Meanwhile, police in Denmark were investigating the disappearance of a top military defector from Iraq, former Gen. Nizar Khazraji, who has aspired to play a lead role in toppling Hussein's regime. The general's son said he feared that Iraqi spies had abducted his father.

But an expert at a think tank in London asserted that Khazraji had gone secretly to the Persian Gulf with the help of U.S. agents to participate in a propaganda campaign to urge Iraqi military defections during an invasion.

Amid preparations for war, the Pentagon confirmed that Rumsfeld had met in Washington with Turkish Defense Minister Vecdi Gonul and discussed ways Turkey might assist in an attack on Iraq. A Pentagon official said about 20 ships carrying equipment and supplies could unload in Turkey if an agreement is reached.

The supplies would be for the U.S. 4th Infantry Division, which was to be a major component of an invasion into northern Iraq until the Turkish parliament voted against allowing American forces to use Turkish bases.

Turkey's government said it would ask parliament to grant the right to use Turkish airspace, but it postponed a separate motion allowing U.S. troops to be based on Turkish soil.

Trying to keep the Turkish army out of Kurdish-controlled northern Iraq, U.S. envoy Zalmay Khalilzad brokered an accord that commits Turkish and Iraqi Kurdish leaders to working together to resolve any ethnic conflicts that may arise during and after an American assault.

The talks in Ankara, the Turkish capital, were aimed at preventing what a U.S. official called a "war within a war."

In London, Blair won a comfortable mandate from the House of Commons by persuading reluctant legislators to endorse a motion backing "all means necessary" to disarm Hussein.

Warning that "this is not the time to falter," Blair predicted that refraining from military force at this point would only encourage other tyrants and weaken the international community.

"Tell our allies that, at the very moment of action, at the very moment they needed our determination, that Britain faltered?" Blair asked rhetorically. "I will not be party to such a course."

About a quarter of the members of Parliament from Blair's Labor Party opposed the motion for war, in an indication of the persistent unease in Britain about invading Iraq without U.N. sanction.

As tensions rose in Baghdad, Hussein presided over a joint meeting of the Revolutionary Command Council, Iraq's highest executive body, and the leadership of the ruling Baath Socialist Party.

"The pathetic Bush was hoping ... to achieve his evil targets without a fight ... which reflects a state of isolation and defeat from which he and his pathetic allies are suffering," the joint meeting declared in a statement broadcast on Al Shabab Television, owned by Hussein's son Uday.

Saddam Hussein went on television in military uniform for the first time since the 1991 Persian Gulf War and told his commanders that Bush's ultimatum was "debased and baseless" and "a sick hope ... that he can win the war without having to fight."

"It is Mr. Bush who should go into exile," he said, "because Mr. Bush is endangering the whole world. It is Mr. Bush and Mr. Blair who should go away and leave their office."

Asked about published reports that U.S. troops were hoping to reach Baghdad in as few as five days, Sabri said that was ludicrous.

"This is not a good joke," he said. "There are other jokes in their psychological warfare better than this one."

Following his meeting with the Revolutionary Command Council, Hussein presided over a session with his senior commanders, including Qusai, his younger son, to review military plans and readiness.

Television and radio urged Iraqis to turn out on short notice for demonstrations organized by the Baath Party.

At the hastily called demonstrations, Iraqis promised to defend Hussein with their souls and their blood.

"Whatever we are able, we will do," declared Haki Ismail, 20, a plumber. "We are not afraid of this war, and it does not matter if it is short or long. Hopefully, America will not dare to invade our land.

"But if they do, we will not let them in here in Baghdad."

Inspectors for the United Nations and the International Atomic Energy Agency, who had been searching for evidence of Iraqi chemical, biological and nuclear weapons, completed their departure Tuesday.

Several embassies emptied, and many foreign journalists left the city.

In Washington, aides said the president assumed that Hussein would not meet the 48-hour deadline that Bush imposed shortly after 8 p.m. Tuesday, Washington time, for Hussein and his sons to step down or face attack.

White House speechwriters prepared a statement for Bush to deliver on national television when he sends troops into battle.

"The president continues to hope, and he knows that the chances are slim, that Saddam Hussein will leave," said White House Press Secretary Ari Fleischer. "But of course, I think everybody hopes that this can be done peacefully. It may not."

Fleischer cautioned Americans not to rule out the possibility that war against Iraq could take longer than some might anticipate.

"The hope is that it would be short ... but I am not prepared to make any predictions about that. I'm not in a position where I can give you any type of certainty about it. I think people have to prepare for the fact that it may not be short," Fleischer said.

"It's just impossible to state."

He and other senior White House aides described Bush as focused and calm about the prospect of war.

"If there are lives lost, he believes the American people understand the risks, the sacrifices that people are prepared to make if it is necessary," Fleischer said. "He is comfortable with the action that is pending and is confident that it will achieve its goal."

Secretary of State Colin L. Powell told international news service reporters that messages had been delivered by other nations urging Hussein to leave, without any result.

"I've also seen some public statements from some countries that suggest he should comply and leave. He has essentially dismissed the message in whatever channel that it has gone," Powell said.

Powell rejected attempts, most noticeably by France, to have the U.N. Security Council address the crisis during a meeting scheduled for today in New York. The French foreign minister planned to attend, but Powell said he would not go.

Powell told reporters that 30 nations had declared varying levels of support for war as part of a "coalition of the willing," and 15 others gave their backing privately.

Bush spoke by telephone with Blair and presidents Vladimir V. Putin of Russia and Hu Jintao of China, according to Fleischer. With both Putin and Hu, the president emphasized cooperation on an array of common issues, despite Russian and Chinese opposition to a U.S. attack on Iraq, the White House press secretary said.

Putin and Bush, who acknowledged their disagreement over Iraq, reconfirmed Bush's scheduled visit to St. Petersburg at the end of May, Fleischer said, adding that Bush thanked Hu for China's role in trying to head off North Korea's nuclear program.

In Moscow, members of the State Duma, or lower house of parliament, protested Bush's move toward war by putting off indefinitely a debate, scheduled for today, on a treaty to reduce deployment of U.S. and Russian long-range nuclear weapons from 5,000 to between 1,500 and 2,200 over the next decade.

Kremlin officials and some lawmakers criticized the postponement. But Igor S. Ivanov, the Russian foreign minister, spoke critically of the United States as he departed for New York to attend the Security Council meeting today on Iraq.

"One must always hope that a chance [for peace] exists, although after Bush's statement, little hope remains," Ivanov said. "We do hope that if the U.S. starts a war against Iraq, the issue will be brought back to the U.N. Security Council soon and fitted into a legal framework for settlement.

"Regrettably, the U.S. has opted to use force, and this choice was made bypassing the U.N.," Ivanov said. "With this choice, the U.S. has taken on the responsibility for this action and for all of the consequences, which will involve enormous casualties and destruction."

In Washington, Powell took note of Ivanov's words but said, "I think Russian-U.S. bilateral relations will survive this disagreement and will continue to thrive, because there is much that pulls us together: our common cause against terrorism, our desire to help the Russian economy, our desire to move forward with" the nuclear weapons reductions.

At the postponement of debate on the nuclear arms treaty, leaders of the State Duma spoke angrily about the possibility of war against Iraq.

"In the event of an American strike against Iraq, the treaty's future will be put into question in general," Duma Speaker Gennady N. Seleznyov told reporters in Prague, the Czech capital, where he was heading the visit of a parliamentary delegation. "The Americans will be striking against international law, and a new period will begin, a period of the law of the jungle, where the strong will trample the weak.

"And we don't want to be weak. Therefore we still need the missiles, because the Americans are afraid of only one thing -- a retaliatory strike. If the Americans were scared by Iraq, which can raise nothing but a smile, let them know that there is a serious nuclear power that can truly guarantee the security of the entire world community and will not permit being subject to the law of the jungle."

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Daniszewski reported from Baghdad and Chen from Washington. Times staff writers Robin Wright, Mary Curtius and Greg Miller in Washington, David Holley in Moscow, Richard Boudreaux in Ankara and Sebastian Rotella in Paris and special correspondent William Wallace in London contributed to this report.